An optical microscope is a device that uses light such as reflected light, transmitted light, and fluorescence emitted from an object to be observed and an imaging optical system of an objective lens, an eye lens, and the like, to magnify images to observe the object. The range observable by an optical microscope at once (hereinafter will be referred to as “the observable range”) is mainly determined by the magnification of the objective lens, wherein the observable range becomes small at the time of high magnification. For this reason, when an objective lens is set to high magnification, an observer may only be able to observe a portion of the range subjected to observation (hereinafter will be referred to as “a range for observation purpose”).
On the other hand, Patent Literature 1 discloses a method of creating an overall image in the range for observation purpose by acquiring an observation image of an object to be observed for every observable range and connecting these observation images, when the observable range is smaller than the range for observation purpose. In this method, an object to be observed is placed on a movable stage, and an imaging optical system (objective lens) is set to low magnification to acquire an observation image in the range for observation purpose. And this observation image is divided into a plurality of small areas, an imaging optical system is changed into high magnification, the movement and stillness of the stage are repeated to arrange all small areas in sequence within the observable range of an imaging optical system, and the observation image of each small area is acquired. Then, the observation images of all small areas are connected to form an overall image of the range for observation purpose.